const html = (verificationCode) => {
  return `
<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>验证码</title>
    <style>
        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }
        
        body {
            font-family: 'Microsoft YaHei', 'PingFang SC', 'Helvetica Neue', Arial, sans-serif;
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            min-height: 100vh;
            display: flex;
            align-items: center;
            justify-content: center;
            padding: 20px;
        }
        
        .container {
            background: white;
            border-radius: 20px;
            box-shadow: 0 20px 40px rgba(0, 0, 0, 0.1);
            overflow: hidden;
            max-width: 500px;
            width: 100%;
        }
        
        .header {
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            color: white;
            padding: 30px;
            text-align: center;
        }
        
        .header h1 {
            font-size: 28px;
            font-weight: 600;
            margin-bottom: 10px;
        }
        
        .header p {
            font-size: 16px;
            opacity: 0.9;
        }
        
        .content {
            padding: 40px 30px;
        }
        
        .welcome {
            font-size: 18px;
            color: #333;
            margin-bottom: 20px;
            text-align: center;
        }
        
        .code-section {
            background: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
            border-radius: 15px;
            padding: 25px;
            margin: 30px 0;
            text-align: center;
            position: relative;
            overflow: hidden;
        }
        
        .code-section::before {
            content: '';
            position: absolute;
            top: -50%;
            left: -50%;
            width: 200%;
            height: 200%;
            background: linear-gradient(45deg, transparent, rgba(255,255,255,0.1), transparent);
            animation: shine 3s infinite;
        }
        
        @keyframes shine {
            0% { transform: translateX(-100%) translateY(-100%) rotate(45deg); }
            100% { transform: translateX(100%) translateY(100%) rotate(45deg); }
        }
        
        .code-label {
            color: white;
            font-size: 16px;
            margin-bottom: 15px;
            font-weight: 500;
        }
        
        .verification-code {
            font-size: 36px;
            font-weight: bold;
            color: white;
            letter-spacing: 8px;
            text-shadow: 2px 2px 4px rgba(0,0,0,0.3);
            font-family: 'Courier New', monospace;
        }
        
        .warning {
            background: #fff3cd;
            border: 1px solid #ffeaa7;
            border-radius: 10px;
            padding: 15px;
            margin: 20px 0;
            text-align: center;
        }
        
        .warning p {
            color: #856404;
            font-size: 14px;
            font-weight: 500;
        }
        
        .footer {
            background: #f8f9fa;
            padding: 20px 30px;
            text-align: center;
            border-top: 1px solid #e9ecef;
        }
        
        .footer p {
            color: #6c757d;
            font-size: 14px;
            margin-bottom: 5px;
        }
        
        .security-tips {
            margin-top: 20px;
            padding: 15px;
            background: #e8f5e8;
            border-radius: 10px;
            border-left: 4px solid #28a745;
        }
        
        .security-tips h4 {
            color: #155724;
            font-size: 16px;
            margin-bottom: 10px;
        }
        
        .security-tips ul {
            color: #155724;
            font-size: 14px;
            padding-left: 20px;
        }
        
        .security-tips li {
            margin-bottom: 5px;
        }
        
        @media (max-width: 480px) {
            .container {
                margin: 10px;
            }
            
            .header, .content, .footer {
                padding: 20px 15px;
            }
            
            .verification-code {
                font-size: 28px;
                letter-spacing: 4px;
            }
        }
    </style>
</head>
<body>
    <div class="container">
        <div class="header">
            <p>您的安全验证请求</p>
        </div>
        
        <div class="content">
            <div class="welcome">
                <p>👋 您好！</p>
                <p>感谢您使用我们的系统</p>
            </div>
            
            <div class="code-section">
                <div class="code-label">您的验证码是：</div>
                <div class="verification-code">${verificationCode}</div>
            </div>
            
            <div class="warning">
                <p>⚠️ 该验证码3分钟内有效，请及时使用</p>
            </div>
            
            <div class="security-tips">
                <h4>🔒 安全提醒</h4>
                <ul>
                    <li>请勿将验证码告诉他人</li>
                    <li>如非本人操作，请忽略此邮件</li>
                    <li>验证码仅用于身份验证，不会要求您转账</li>
                </ul>
            </div>
        </div>
        
        <div class="footer">
            <p>此邮件由系统自动发送，请勿回复</p>
            <p>如有疑问，请联系2743537306@qq.com</p>
        </div>
    </div>
</body>
</html>`;
};

module.exports = html;
